The present invention relates to a DC/DC converter for operating a load, especially an electrical load comprising light-illuminating diodes or LEDs.
Constant-current sources are primarily used to control an electrical load, especially a load of LEDs, LED chains and/or LED arrays. Diverse arrangements of LEDs are known; besides parallel and matrix connection of LEDs, the possibility of series connection of LEDs is known. In a series connection of LEDs, all LEDs are connected behind one another in a row; this connection is also called an LED chain. In order to operate LED chains, a constant current is generated and conducted through the LEDs. A voltage that corresponds to the sum of the forward voltages of all LEDs then appears across the LEDs.
To achieve a constant luminous efficacy, the current that flows through the LEDs must be controlled in a temperature-dependent manner and nearly constant. This control is achieved in a known manner using pulse width modulation of the supplied current. This modulated current is then used for brightness control of the LED chain by means of pulse width modulation.
The energy supply of the LEDS is accomplished, for example, by means of a step-up converter.
An LED cluster arrangement that is supplied with constant current is known from DE 20 2007 011 973 U1. The LED cluster arrangement is controlled by pulse width modulation.
DE 2006 059 355 A1 discloses a control device in a method for operating a series connection of light-emitting diodes.
DE 10 2005 058 484 A1 discloses a circuit arrangement and a method for operating at least one LED.
Problematic in the known state of the art, however, is that a substantial expense is required in regard to the number of components to be used and in regard to the brightness control of the LEDs. In particular, the known prior art disregards high flexibility in regard to the ratio of input voltage to output voltage considering the usually necessary level of the output voltage to be achieved.